ABSTRACT

Assessment of the level of Heavy metals such as copper, Chromium, Cadmium, Lead, Zinc, Iron and Nickel in soil samples from Koro-koro (polluted soil samples) and Kpite community (Control soil sample), in Tai Local Government Area, Rivers State, Nigeria were investigated. Studied samples were collected from two different location. The samples were air dried for 2 days after which it was oven dried for 3 hrs. 1g of each dried samples were weighed on a top loading balance after which they were digested with 20ml aqua regia (Conc. HCL + HNOȝ) solution. The presence of Cu, Fe, Zn, Cr, Cd, Ni and Pb were analyzed in samples using Atomic Absorption Spectrophotometer (AAS) in accordance with AOAC, official methods. The concentration of Fe, Zn, Cu and Cr were found to be high in both soil samples above the WHO limit.

However, concentration of Pb (16.6mg/kg) was 10-14 times high than that of the average agricultural soils in the polluted sample which will pose high risk to the environment. The levels of Cd (<0.05mg/kg) in the polluted sample was below detection limit. And the levels of Ni concentration in both samples was (<0.05) below detection limit. The pH was slightly alkaline in the polluted soil.

Heavy metals such as Fe, Cu and Cr were assessed to contained high contents in both samples above WHO limits, it can therefore be concluded  that the sols are polluted directly (due to industrialization) and indirectly (due to improper disposal o material i.e steel, etc) which are indicative of environmental pollution. Although the essential elements are beneficial to plants. When found in excessive amounts well above acceptable levels in soils which can be uptake by plant, they can be detrimental and pose high risk to health.

CHAPTER ONE

1.0          INTRODUCTION

1.1          BACKGROUND OF STUDY

The daily industrial activities on the earth surface result in soil pollution, thereby increasing the levels of heavy metals in the soil. Heavy metals all not only toxic, but have cumulative or Synergistic effects on both terrestrial and aquatic resources (Lameed and Ayodele. 2008. Muwanga and Barifaijo, 2016). The concentration of heavy metals in large quantities induces many biochemical and chemical changes in the soil systems (Kabir et al, 2010), which in the long run may inhibit plant growth.

Heavy metals are currently of much environmental concern. They are harmful to humans, animal, plants and the susceptible to bioaccumulation on the food chain. Heavy metals may come from many different sources in urban areas. Atmospheric pollution is a major contributor of heavy metal contamination in top soils (Kelly et al, 1996).

Heavy metals mix with the substances existing in such upper layers and change their characteristics. Soil reaction (pH), condition a mobile form of heavy metal amounts and organic substances in sediments acting like a buffer and storing these materials for a long time.

The degree of the heavy metal accumulation in surface sediments depends in different emission sources and distance between them. Heavy metal is one of the important pollutants in the environment as a result of both natural and anthropogenic activities. Wastewater irrigation. Solid waste disposal, sludge applications, vehicle exhaust and industrial activities are the major sources of soil contamination with heavy metals and an increased heavy metal uptake by food crops grown on such contaminated soil often observed. Heavy metals have a potential to contaminate soil, which can be dispersed and  accumulated in plants and animals, and taken in by humans through consumption (Zhang et al:2008, Wang and Zhang 2012).

One of the main environmental impacts of industry is the progressive change in the chemical composition of ecosystem located around emission sources continous release of heavy metals from anthropogenic sources causes significant changes in the biochemical cycle of those elements (Miskowree et al, 2014).

Heavy metals have the potential to contaminate soil, which can be dispersed and accumulated plants and animals and taken in by human through consumption (Zhang et al, 2008, Wang et al: 2012). So heavy metals contamination has been a world wide environmental concern with its potential ecological effect (An, 2006).  The presence of heavy metals in water (lakes, river and sea), air dust, soils and sediments plays an important role in human life (Juvanovic et al: 1995, Cheng et al, 2013). Heavy metals all important toxicity sources for soils. And heavy metals contamination of soil is based on three main. Sources: road traffic (automobile), industrial activities and weathered material (Abu-ulaban et al, 2003. In terms of roadside soil, the most effective contaminant source is vehicle traffic. Soil contamination by heavy metals, poses a risk to the productivity capacity and the balance of the ecosystem. The soil has a diverse heavy metal concentration that is dependent on the parent material on which it is formed. The formation processes and the composition and proportion of the components of the solid phase (fadigas, 2002, Alleoni et al, 2005).

The effect of this contamination may be reflected in the plant behavior, microbiological processes and the transfer of toxic levels of the elements to man and animals (Nicholsm et al, 2003).

Soil as an essential natural element represents a very complex system sensitive to different influences. Human activities  have dramatically changed the balance and biochemical and geological cycles of many heavy metals.

An assessment of environmental risk caused by soil contamination is especially important for agriculture as well as non-cultivated area due to the fact that metals are potentially harmful to human health persist in soils for relatively long time and many transfer into the food chain in considerable amounts ( szynkowska et al ,2009].The content of heavy metals in soil and their impact  on ecosystem can be influenced by many natural factors such as parent material, climate and  soil processes ,and anthropogenic activities such as industry, agriculture and transportation.

1.2          STATEMENT OF THE PROBLEM

The people of Koro-koro community in  Tai  Local Government rely on the produce from their  farms.The  presence of high concentration of heavy metals in  the soil of Koro-koro community in Tai Local Government Area causes soil pollution due to excessive oil spillage. The effect of this heavy metals pollution may be reflected in plant’s behaviour, microbiological processes and the transfer Tai Local Government Area, Rivers State. The people in the area have experienced oil spill from 2000 till date, which have polluted the environment and has prevented the people in the area from farming. The main occupation of this people is farming but due to the oil pollution, it has affected their source of living. Heavy metals have a potential to contaminate soil which can be dispersed accumulated in plants and animals, and take  in by humans through consumption which result the devastation of human health especially to the people of Koro-Koro community in Tai Local Government Area.

1.3          AIM AND OBJECTIVE OF THE STUDY

The key objective of this research work is the assessment of the level heavy metals, in polluted soil of Koro-Koro community in Tai Local Government Area. The following specific objective area also to be put under consideration.

1. To conduct and identify the heavy metals that are associated with the pollution of the soil.
2. To compare the level of heavy metal in polluted soil with the world Health Organization Standard.

1.4          SIGNIFICANCE OF THE STUDY

The data from this research will serve as a benchmark for further work on accumulation of heavy metals in Koro-Koro farmland . it will also serve the purpose of awareness to consumers of crops harvested from polluted soil and the potential Health implication.

The people of Koro-koro community will benefit more based on the advice that will given to them on how to address the issues of heavy metal pollution.

1.5          SCOPE OF THE STUDY

The scope of this study is centered on the assessment of the level of heavy metals in polluted soil from Koro-koro community in Tai Local Government Area, Rivers State.